Plastic materials have been used broadly for packaging or carrying substrates and the like. However, their chemical permeability is not as good as those of inorganic glass sheets or metal sheets. There is general interest in improving the barrier properties of plastic sheets. On the other hand, there is also broad interest in thin, conformable packages for devices made on glass substrates or single crystal wafers. There is also interest in thin barrier coated paper for flexible substrates or package materials.
For such conformable packages being used for electric, electronic or opt-electronic devices, picture frames, craftworks, plastic-containers, stamp collections, etc., they should have a small coefficient of thermal expansion, as well as superior permeability to water, oxygen, gas and ozone. In many cases, the packages should also have high optical transparency, good surface flatness and chemical resistance. Glass plates have been used in many of these applications; however, they are fragile and easy to break under external force, which disqualified them for many commercial applications due to safety regulation. In some cases, the glass plates are too heavy to be used.
Plastic plate is advantageous over the glass and silicon wafers in terms of weight and design flexibility. In addition, an economic advantage for using plastic plate as containers, picture frames, craftworks, stamps collections, etc. is from their continuous manufacturing.
Organic/polymer based devices are rapidly gaining momentum as the technology of choice for optoelectronic and electric applications where low power consumption, low cost and superior ability to build on plastic substrates are desired. However, systematic studies demonstrate that organic/polymer based devices degrade when they are exposed to oxygen, water vapor or UV light. For example, substantial degradation in organic light-emitting diodes (OLEDs) and polymeric lighting-emitting diodes (PLEDs) occurs, due to the instabilities of the organic/polymer materials and/or their interfaces with the contact electrodes when subjected to moisture, oxygen and/or ozone. Additionally, the metals used for the electrodes in OLED devices are rapidly reactive to water and oxygen.
Raw plastic substrates are generally too permeable to moisture and oxygen to be used in packaging for organic/polymer based devices. For example, the oxygen and water permeabilities in a 12 μm thick PET film are ˜1.5 ml/m2/day and 1.5 g/m2/day, respectively. Therefore, one ongoing research interest is focused on developing a flexible substrate or encapsulation layer with low water and oxygen diffusivities.
Papers are another class of materials with promise for use as thin film substrates. Since papers are typically made with fabric materials, additional coatings are typically need to provide the necessary barrier properties. Various methods and techniques have been devised for development of a coating layer or layers for protecting against oxygen, water, and ozone permeation.
In the food industry, co-extruded laminate films have became increasingly important and have recently been applied in the packaging of products such as fresh pasta, meats and cut vegetables to extend the self-life of the goods. Commercial multilayer films currently comprise a number of layers of different polymers. In most applications, the outer layer consist of cheap, water barrier polymers with good mechanical properties and the inner layer consist of more expensive materials, which offer good gas-barrier properties. However, the permeability of package films in food industry is not sufficient for the applications addressed in this invention.
For display applications, a hermetic encapsulation technique using a glass or metal lid attached by a bead of UV cured epoxy resin has been proposed to protect OLEDs/PLEDs from oxygen and water vapors (P. E. Burrows, V. Bulovic, S. R. Forrest, et al., Appl. Phys. Lett., 1994, 65, 2922). However, these types of seals are expensive to fabricate and require extensive labor to assemble. In addition, these seals are large and heavy so that they severely limit the application of the OLEDs/PLEDs. For thin and lightweight passivation of OLEDs/PLEDs, encapsulation methods based on dry processes have been proposed (K. Yamashita, et al., Appl. Phys. Lett., 2001, 34, 740; S. H. Kwon, et al., Appl. Phys. Lett., 2001, 79, 4450; M. S. Weaver, et al., Appl. Phys. Lett., 2002, 81, 2929; WO Patent, No. 02/063698; US patent, No. 2002125882; US patent, No. 2005/0227004; US. Patent, No. 2005/0239294; WO Patent, No. 98/01910; U.S. Pat. No. 6,873,101). B. Nilsson and P. Bailey disclosed a thin film packaging method comprising one or more thin dielectric layers (e.g., SiN4) processed with PECVD at low temperature (U.S. Pat. No. 6,635,989).
Vitex System Inc. developed a thin package film in a multilayer structure termed Barix for encapsulating OLEDs (L. Moro, et al., SPIE, 2004, 5214, 83; US Patent Application Publication No. 2002/125822). The Barix developed by Vitex Systems Inc. includes deposition of Al2O3 layers, which are reactively sputtered onto the display via energetic plasma, in between polyacrylate layers deposited via flash evaporation for the monomer followed by UV curing. The entire process is carried out in a bulky integrated vacuum tool, so that process size is limited and cost is high.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide new and improved multilayer films for packaging applications.
It is another object of the present invention to provide new and improved methods of manufacturing multilayer films for packaging applications.
Another object of the invention is to provide new and improved multilayer films that are easy to produce and install as packages.
Another object of the invention is to provide new and improved multilayer films that produce a high permeation barrier to water, oxygen and ozone.
Another object of the invention is to provide new and improved multilayer films that are solution-processed to simplify manufacturing.